1. Technical Field
The present disclosure relates to a charge pump stage, a method for controlling the charge pump stage, and a memory comprising the charge pump stage, such as a charge pump stage with reduced consumption and to a method for controlling supply of the charge pump stage.
2. Description of the Related Art
As is known, charge pumps are typically used in circuits that have internal operating voltages higher than a supply voltage VDD. For instance, in the case of circuits that manage nonvolatile memory cells of an EEPROM type, the supply voltage of the circuits responsible for reading said cells are generally comprised in the range of 2.2-4.5 V. In the case of memory cells of a FLASH type, the range of supply voltage is approximately 4-6 V. The programming and erasure voltages are approximately 12-15 V, whilst the supply voltage VDD is generally comprised between 1 V and 4 V. Operation of a charge pump is based upon the charge transfer from a supply terminal (biased at the supply voltage) to an output stage of the charge pump, which comprises an accumulation capacitor configured for accumulating a charge such as to generate across it the desired output voltage VOUT. Said output voltage depends upon the charge transferred. In order to regulate automatically the amount of current supplied to the accumulation capacitor to keep the voltage VOUT across it relatively constant, it is common to use a voltage-regulator circuit configured for detecting the voltage VOUT at output from the charge pump (or, more typically, a voltage proportional to the output voltage) and control in feedback the current supplied to the accumulation capacitor in order to maintain the output voltage VOUT at a desired regulation value VREG.
Operation of a regulator circuit generally envisages comparison of a partition of the output voltage VOUT with a reference voltage VREF (generated by means of a bandgap circuit of a known type). The result of said comparison is a state signal, which indicates that a desired level of output voltage VOUT has been reached and is configured for acting on the charge pump for interrupting charge transfer to the accumulation capacitor.
FIG. 1 shows a regulator circuit 1, of a known type, configured for generating at output a signal for enabling charge transfer VON/OFF and connected to a charge pump 2, which is also of a known type, which is connected to a supply terminal 3, from which it receives the supply voltage VDD, and is configured for receiving on an input terminal 2a the signal for enabling charge transfer VON/OFF and generating a charge signal VOUT on an output terminal 2b. According to an embodiment of a known type, the regulator circuit 1 comprises a comparator 4, configured for receiving on a first input 4a a reference signal VREF and on a second input 4b the output signal VOUT (or, typically, a comparison signal, not shown, given by a partition of the output signal VOUT), and for generating at output the signal for enabling charge transfer VON/OFF on the basis of the comparison between the partition of the output signal VOUT and the reference signal VREF.